The present invention relates to a dock leveler or bridging device that includes a bridge plate that is pivotably connected to a dock. The bridge plate can be raised via a lifting cylinder, and can be lowered by its own weight. The free end of the bridge plate is provided with a movable extension that can be retracted or extended via a feed cylinder for removal from or placement upon a platform that is to be loaded or unloaded.
With bridges of this type, the lifting cylinder for pivoting the bridge plate is provided with only a single pressure line that is disposed at the bottom. This line is pressurized when the bridge plate is to be raised. Lowering of the bridge plate is effected via the weight of the bridge plate itself, with the pressure medium being expelled from the lifting cylinder. With the heretofore known bridges, such a lowering movement requires special control and switching means.
It is an object of the present invention to provide a bridging device of the aforementioned general type where the control and switching means can be embodied in a particularly straightforward manner in cooperation with the two pressure lines of a reversible pump.